1. Field of the Invention
Preferred embodiments of the present invention generally relate to an information embedment manner, and more particularly, to an image processing apparatus, an image processing method, and a program product that embed information in image data.
2. Discussion of the Related Art
Recent trends toward converting information into electronic data show no signs of abating, and image forming apparatuses and image processing apparatuses, such as printers, facsimiles, and so forth, have been indispensable in outputting information converted into electronic format.
Typically, such an image processing apparatus is configured as a composite apparatus that can be employed as a printer, a facsimile, a scanner, a copier, or the like, by including shooting, image formation, communications, and other such capabilities. In such an image processing apparatus, a commonly known technique to embed supplemental information in image data is employed to control copying of digital data, to associate digital data with printed data, and so forth, and a variety of methods to embed information in image data have been proposed.
For example, a method to embed information in image data by using spaces between characters, a method to superimpose a visible dot pattern on image data, and a method to embed information invisibly by modifying a background image of original image data are commonly known. It is to be noted that a method to embed information in image data is required to be selected based on the type of information and the intended use or purpose of image data to be generated by embedding the information.
For example, a technique to select an appropriate information embedment method has been proposed. In the technique, image data is converted into frequency components and an appropriate information embedment method is selected depending on data volume of high-frequency components.
In addition, another technique has been proposed in which a copyright protection mode or a manipulation detection mode is selected in embedding information in original image data, and strength of information embedment varies according to the selected mode.
However, these techniques have a drawback in that there is no way to ensure that the most appropriate information embedment method is selected. By embedding information in original image data, a variety of functions, such as copy restriction, trace, manipulation detection, and so forth, are provided depending on the purpose for which image data is to be generated by embedding the information. A selected information embedment method using the above-described techniques may not satisfy those functions required by a user.
At the same time, even when an appropriate information embedment method is selected, because an information volume of embedment information varies depending on information embedment methods, when the image data does not have enough area to include the embedment information, the embedment information cannot be embedded in the image data. Furthermore, even when embedment information is embedded in image data, the embedded information may affect generated image data depending on the way in which the embedded information is embedded.
On the other hand, another technique to embed required information in image data by applying image processing to original image data has been proposed. In this technique, when required information cannot be embedded in image data, the required information is forcibly embedded in image data by degrading image quality or resistance of generated image data. However, this technique is limited to enforced embedment of invisible information, and visible information cannot be embedded forcibly.
Further, another technique to embed required information in image data by image-processing original image data has been proposed. In this technique, required information is embedded in spaces between characters on a document image of image data. However, when image data cannot include required information, the required information cannot be forcibly embedded in the image data.